I had the same issue where I could not view VU+ Duo channels remotely/ I eventually sorted it out with the following step.
I used port 81 for VU+ Duo instead of the standard port 80. When I locally connected to VU+ Duo through my PC everything worked fine and I could stream videos using VLC without any problem using the address 192.168.1.xx:81
However , using the no-ip.org DNS service , after forwarding port 81 in the router, I managed to log into the Webif remotely but no video streaming was possible through VLC. The error was in VLC streaming. When I viewed the error log , I noticed that VLC was using the URL and port 80 although I typed myname-no-ip.org:81 in the browser address. I could not figure out nor did I find a solution for VLC insisting on translating my port from 81 to the standard http port 80. However, a helpful site recommended that port 8001 and 554 be also be forwarded for remote viewing.
I followed that instruction and wallah , it worked. I can now remote view my VU+ Duo using myname-no-ip.org:81 . Of course for the newbie , you need to subscribe ito a DNS service like mine of DDNS.com
Unfortunately, I do not have the technical knowhow to decipher what has gone on in my case, suffice to say it is working hoping that similar step might help others.